Spiraling Spin Structure in an Exchange-Coupled Antiferromagnetic Layer

Using trilayers of permalloy/FeMn/Co with various thicknesses $t_{\mathrm{AF}}$ of the antiferromagnetic FeMn, we have observed evidence of a spiraling spin structure within FeMn. For $t_{\mathrm{AF}}<90\mathrm{}$ Å, the turn angle $\theta$ of the spiral varies as $\theta =\left(1.76°/Å\right)t_{\mathrm{AF}}$.